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Speed controller smoke

Hey there, Recently got into the modified scooter world and am loving it. I got a gt 350 scooter with a currie 24v 350w motor on it. I overvolted to 36v and have been riding fine for a few weeks now. Tonight, I noticed that the 24v speed controller was smoking and saw some burn marks on the speed control board when I disassembled. Manufacturer sealed the board up good. Can anyone tell me what burned up?
Usually it is the MOSFET transistors that burn out, however it could be almost any other component on the board as well. If a MOSFET burned out then usually the motor will run at full speed no matter what the position of the throttle is.

Don't know why this is happening - bad controller?

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Hi Rob,

I watched your video and it sounded like the motor was having a hard time running. I am not sure if that is because of the motor, wheel, axle, bearings, or controller though. A controller overheating problem like that is almost always due to a motor with too much physical resistance on it, or burned out or faulty motor windings, so I would start with troubleshooting the motor.

I would begin troubleshooting by unplugging the motor from the controller and spinning the skateboard wheel with your hand to see if it spins easily or if there is a lot of resistance when trying to spin it. The wheel should spin easily and without very much resistance.

The next diagnostic test to perform would be to unplug the motor and battery from the controller. Then put a pair of leather work gloves on and then connect the motor wires directly to the battery. There should be a large spark when making the final connection which is normal and nothing to worry about. Be ready to unplug the motor wires from the battery quickly if they get hot (that is the reason for the gloves). During this test the motor should spin the wheel very fast and the wheel should get up to speed almost immediately. I would keep the motor running for a little while during this test and see if the motor wires get warm or hot.

The motor wires should remain cool during this test no matter how long the motor is running for. If the motor wires get warm or hot then there is either something causing too much physical resistance with the motor or wheel such as bad bearings or some other type of mechanical problem which is applying too much drag on them, or the motor has burned out or defective windings which is causing too much electrical resistance on the system.

Please let us know how it goes after performing these tests.

Here's the motor movie - seems to be fine.  Thoughts?

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(5.21 MB)
That motor looks to be running just fine in the video. It hardly even made a spark when touching its wire to the battery so it is not drawing very much power at all and could not be causing the controller to smoke like that.

Do you know if maybe the battery was wired in reverse polarity to the controller at one time, or if any of the wires were momentarily short circuited when testing the controller?

We've been very careful to make sure the connections are correct.  No wires crossed.



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